Conventional adjustable metal shelving commonly includes set screws for anchoring the shelves at selected elevations. The screws are turned until they tightly engage the metal corner posts. Overtightening of the screws could damage the posts or, in some cases, strip the threads of the screws. On the other hand, should the screws be too loose, or should they become loosened during use, the stability of the entire structure could be affected and the equipment or articles supported by the loosened shelf could fall and become damaged. Furthermore, the set screw arrangement, while offering an advantage of infinite adjustability, also has the disadvantage of providing little or no indication of just when a shelf is level, thereby presenting a real possibility that such a shelf might be tightened while in a slightly tipped condition, with consequential effects on the alignment and stability of the assembly as a whole.
U.S. Pat. Nos. 3,280,767 and 3,344,756 illustrate constructions in which set screws directly engage the corner posts to hold the shelves in position. A modified construction in which a set screw is used but does not directly engage the post is disclosed in U.S. Pat. No. 3,747,540. U.S. Pat. Nos. 3,424,111, 3,523,508, and 3,757,705 teach constructions in which set screws are eliminated and the shelves are held in place upon circumferential grooved posts by sleeves equipped with portions receivable in the grooves. Co-owned U.S. Pat. No. 3,589,746 teaches a system in which the shelves are locked in place with friction corner braces.
Co-pending co-owned application Ser. No. 576,038, filed May 9, 1975, now U.S. Pat. No. 3,964,404, discloses a shelf and corner post construction in which the outer aspect, or outer surface portion, of each post is smooth and is slidably engaged by the perimetric frame of the shelf. The inwardly-facing surface of the post is provided with a series of vertically-spaced recesses or indentations. A brace bridges the adjacent side members of the perimetric frame, the post extending through the space between the corner section of the frame and the brace. A screw, threadedly carried by the brace, urges the arms of a U-shaped clip into the indentations of the post to wedge the parts into tight locking relationship.